1. Field of the Invention
The present invention relates to a parallel link robot and, more particularly, to a parallel link robot having joint portions.
2. Description of the Related Art
In the past, there is known a parallel link robot that includes a plurality of arms arranged side by side and capable of being bent and stretched in joint portions (see, e.g., Japanese Patent Application Publication No. 2011-194534).
JP2011-194534A discloses a parallel link robot including a first arm having a first joint portion, a second arm having a second joint portion engaging with a first engagement portion, and a biasing mechanism unit for biasing the second joint portion toward the first joint portion. Each of the first joint portion and the second joint portion includes a spherical portion and a concave portion engaging with the spherical portion and makes up a ball joint mechanism. The biasing mechanism unit biases the concave portion against the spherical portion, thereby keeping the concave portion and the spherical portion engaged with each other. The parallel link robot is configured such that, if an external force larger than the biasing force of the biasing mechanism unit is applied to the arms, the first joint portion and the second joint portion are disengaged from each other. This helps prevent the parallel link robot and other equipment from getting damaged during occurrence of an abnormality.
The biasing mechanism unit of the parallel link robot disclosed in JP2011-194534A includes a closed-bottom cylindrical bush (a first connection member) attached to a joint section of the second arm having the second joint portion, the bush fitted to a cylindrical columnar engaged pin provided in the joint section so that the bush can cover the engaged pin, a hook-shaped connector engaging with the bush, and a coil spring for biasing the connector toward the first joint portion.
In the parallel link robot disclosed in JP2011-194534A, however, the biasing mechanism unit is attached through the bush (the first connection member) fitted to the engaged pin of the joint section. Therefore, if the first joint portion and the second joint portion are disengaged from each other under the action of an external force, the bush is removed from the engaged pin. This poses a problem in that the biasing mechanism unit is easily removed. In the event that the parallel link robot is used in picking foodstuffs, medicines, cosmetics and so forth, the removed components may possibly be mixed into a production line. From the viewpoint of sanitation, it is required to reduce the likelihood of removal of the components as far as possible.